Test Method for Shear Thinning Index of Non-Newtonian Liquids Using a Rotational Viscometer

Rheological properties of mixtures of hydroxypropylmethyl cellulose (HPMC), a nonionic associative cellulose ether, and sodium dodecylsulfate (SDS), an anionic surfactant, were investigated by viscosity measurements performed at different shear rates (0.1-6000 s-1). HPMC/SDS mixtures containing different concentrations of SDS (CSDS=0.00-3.50 % w/w) and HPMC concentrations which corresponded to the overlap parameter c/c*=3, 6, and 12 were prepared. All HPMC/SDS mixtures were found to be shear-thinning when examined in a low-end-to mid-range of the applied shear rates. The degree of shear-thinning, n, and viscosity of the mixtures were influenced by composition of HPMC/SDS mixtures and HPMC-SDS complex formation. The changes in n ranged from values typical for highly shear thinning to almost perfectly Newtonian liquids, and were more pronounced as c/c* was increased from 3 to 6 and 12. A change in flow profile and a buildup of the first normal stress difference (N1) was observed in HPMC/SDS mixtures with c/c*=6 and 12 and CSDS 0.55-1.00 % and 0.55-2.50 %, respectively, when a critical shear rate, crit. was exceeded, suggesting that a shear-induced structure formation in the mixtures took place.

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Test Method for Low-Temperature Viscosity of Automatic Transmission Fluids, Hydraulic Fluids, and Lubricants using a Rotational Viscometer

10.1520/d2983-21 ◽

2021 ◽

Author(s):

Keyword(s):

Low Temperature ◽

Automatic Transmission ◽

Test Method ◽

Rotational Viscometer ◽

Hydraulic Fluids

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Surface-tension-driven breakup of viscoelastic liquid threads

Journal of Fluid Mechanics ◽

10.1017/s0022112082002754 ◽

1982 ◽

Vol 120 ◽

pp. 245-266 ◽

Cited By ~ 54

Author(s):

Simon L. Goren ◽

Moshe Gottlieb

Keyword(s):

Relaxation Time ◽

Stress Relaxation ◽

Polymer Solutions ◽

Small Diameter ◽

Shear Thinning ◽

Prior History ◽

Axial Tension ◽

Dilute Polymer Solutions ◽

Linearized Stability ◽

Newtonian Liquids

A linearized stability analysis is carried out for the breakup of small-diameter liquid filaments of dilute polymer solutions into droplets. Oldroyd's 8-constant model expressed in a corotational reference frame is used as the rheological equation of state. The crucial idea in this theory is the recognition that the liquid may be subject to an unrelaxed axial tension due to its prior history. If the tension is zero, the present analysis predicts that jets of shear-thinning liquids are less stable than comparable jets of Newtonian liquids; this is in agreement with previous analyses. However, when the axial tension is not zero, and provided the stress relaxation time constant is sufficiently large, the new theory predicts that the axial elastic tension can be a significant stabilizing influence. With reasonable values for the tension and stress relaxation time the theory explains the great stability observed for jets of some shear- thinning, dilute polymer solutions. The theory explains why drops produced from jets of such liquids are larger than drops from corresponding Newtonian liquids. The theory also appears capable of explaining the sudden appearance of irregularly spaced bulges on jets after long distances of t,ravel with little amplification of disturbances.

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Rheological Behavior of Glycyrrhiza glabra (Licorice) Extract as a Function of Concentration and Temperature: A Critical Reappraisal

Foods ◽

10.3390/foods9121872 ◽

2020 ◽

Vol 9 (12) ◽

pp. 1872

Author(s):

Laleh Nasiri ◽

Mohsen Gavahian ◽

Mahsa Majzoobi ◽

Asgar Farahnaky

Keyword(s):

Experimental Data ◽

Flow Behavior ◽

Shear Thinning ◽

Soluble Solids ◽

Licorice Root ◽

Rotational Viscometer ◽

Unit Operations ◽

Licorice Extract ◽

Solids Content ◽

First Time

In the present study, rheological properties of twelve different licorice root extracts were evaluated using a rotational viscometer as a function of soluble solids content (15–45 °Bx) and temperature (30–70 °C). Response Surface Methodology was used to understand the relationships between the parameters. The experimental data were then fit into mathematical models. The results, for the first time, revealed that the licorice solutions had non-Newtonian shear-thinning behaviors with flow behavior indexes of 0.24 to 0.91, depending on the licorice extract samples, temperature, and °Bx. These observations were different from those reported in the literature and the present study elaborated on reasons for such observations. Further, the shear-thinning behavior generally increased by increasing the °Bx and decreasing the temperature. In addition, the power-law model was found to be suitable for predicting the experimental data. The newly revealed information can be particularly important in designing the unit operations for licorice extract processing.

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Empirical Modelling of Nonmonotonous Behaviour of Shear Viscosity

Advances in Materials Science and Engineering ◽

10.1155/2013/658187 ◽

2013 ◽

Vol 2013 ◽

pp. 1-4 ◽

Cited By ~ 7

Author(s):

J. David ◽

P. Filip ◽

A. A. Kharlamov

Keyword(s):

Shear Viscosity ◽

Extreme Points ◽

Shear Thickening ◽

Local Maximum ◽

Shear Thinning ◽

Algebraic Form ◽

Complex Behaviour ◽

Empirical Modelling ◽

Newtonian Liquids ◽

Almost All

Almost all hitherto proposed empirical models used for characterization of shear viscosity of non-Newtonian liquids describe only its monotonous course. However, the onset of new materials is accompanied by more complicated characteristics of their behaviour including nonmonotonous course of shear viscosity. This feature is reflected not only in an existence of one extreme point (maximum or minimum), but also it can appear in both extreme points; that is, this shear viscosity initially exhibits shear thinning; after attaining a local minimum, it converts to shear thickening, and again after reaching a local maximum, it has a shear-thinning character. It is clear that, for an empirical description of this complex behaviour, a hitherto, used number of parameters (four, five) in classical monotonous models (such as Cross or Carreau-Yasuda) are no longer tenable. If more parameters are applied, there should be given an emphasis on a relatively simple algebraic form of the proposed models, unambiguity of the involved parameters, and their sound interpretation in the whole modelling. This contribution provides an overview of the existing empirical nonmonotonous models and proposes a new 10-parameter model including a demonstration of its flexibility using various experimental data.

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